Inputs on Comp

I'm sort of a noob when it comes to computers, so I need to ask a question, since my friends can't figure this out and the manual has nothing regarding this.  My computer has  inputs on it(Composite and S-Video, and another with progressive), and I want to hook up my Ps2 to it so I can play games and make it show on my pc screen.  The problem is, when I hook it up to the inputs, I don't know how to access the input video(channel, line,forgot what you call it).  I want to know how I can access it, and if I need a certain program to do so.

Related question, dont wanna make a new thread: Anyone got a XM radio? i got one for free through a promotion, and i wanted to configure my ATI All In Wonder to accept it as the RCA input. i used the supplied cable, but i dont see where one is supposed to actually get that feed to respond to..well, anything at all. where are the controls for audio on the all in wonder cards?